(1) Field of the Invention
This invention relates to four element torque converters providing plural power paths between the torque converter and an associated transmission, and in particular for the lock-up clutch employed in such a torque converter.
(2) Description of the Related Art
In conventional four element torque converters of the type provided by this invention, an input shaft to the torque converter drives the impeller of the converter. The impeller fluidically drives a primary and secondary turbine of the torque converter which both in turn drive primary and secondary input shafts to the associated transmission mechanism. These torque converters also commonly employ a stator coupled to the transmission housing through a one-way clutch.
In the prior art torque converters of this type, if a direct drive to the transmission assembly bypassing the torque converter is desired, it is common practice to provide a direct drive clutch coupling one of the primary or secondary turbines and their associated shafts to the input shaft of the torque converter. Alternatively, a separate or third input shaft separate from the shafts of the primary and secondary torque converter turbines would be provided to be directly clutched to the torque converter input shaft to provide the direct drive to the transmission assembly bypassing the torque converter fluid coupling.
The former of these methods of providing a direct drive bypassing a four element torque converter limits the type of transmission gearing assembly that could be employed with the four element torque converter to one adapted to receive only one direct drive input to the transmission gearing assembly. The gearing of the transmission assembly driven by the torque converter turbine that could not be directly clutched to the input shaft of the torque converter could not be utilized in the direct drive speed ratios.
Those transmissions employing a third concentric shaft for direct drive bypassing the four element torque converter require a more complex transmission assembly and more space for that assembly to provide for the third input shaft.
The present invention seeks to solve these problems by providing an improved lock-up clutch for a four element torque converter which provides a direct drive input from the input shaft of the torque converter to the primary and secondary transmission input shafts, thereby providing direct drive to the associated transmission gearing arrangement without requiring a third input shaft.